search for: rwsem_waiting_bia

Btrfs uses an rwsem to control access to its extent tree. Threads will hold a read lock on this rwsem while they scan the extent tree, and if need_resched() they will drop the lock and schedule. The transaction commit needs to take a write lock for this rwsem for a very short period to switch out the commit roots. If there are a lot of threads doing this caching operation we can starve out the